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A reliable assessment of the availability of bioresources represents the first step to defining local value chains of particular interest. More than 190 and 50 Mt/y of bioresources are currently available in Europe and Italy, respectively, even if they are not fully valorized. The best end use of these feedstocks is strictly dependent on specific territorial/regional peculiarities, that consequently affect the products' final properties. In this work, the Italian web-GIS-based tool “Atlante delle biomasse” was used to determine the availability of many bioresources in Italy at the regional level. A lump classification criterion was used to categorize the available biomasses, and, then, an optimization algorithm based on a process superstructure was applied to find out the available fraction of bioresources, the amount of biofuels potentially obtainable and, consequently, the regional fuel demand coverable by biofuels. In particular, only the energy-self-sufficient technologies with higher TRLs were considered in the mathematical model. The integration between the different selected bioresources led to three biofuels to be considered, evaluating the percentage of biofuel demand that could be covered for each Italian region. The final potential production of biofuels derived from local bioresources in Italy settles down on the range 9 107 – 1.6 108 GJ/y covering about 5, 50, and 100 % of methane, biodiesel and bio-LPG demand respectively. Bio-LPG demand for all regions was to be considered completely satisfied, biodiesel production was also sufficient to cover high demands, on the other hand, low values of biomethane requirements coverable were obtained. [ABSTRACT FROM AUTHOR]

There is an urgent need for research efforts aimed at developing technologies capable of efficiently gasifying sustainable biomasses composed of organic waste from various industrial processes. This work constitutes a crucial contribution to the field by addressing the pressing need for sustainable biofuels production. It introduces an innovative open-source mathematical model, implemented in Python, designed to simulate the complex process of gasifying advanced biomasses within a downdraft gasifier. Termed the “bi-equilibrium with tar cracking” model, it represents a significant advancement in the modelling of biomass gasification, offering a versatile and comprehensive tool for researchers and engineers in the field. The model’s multi-zone framework is particularly noteworthy, as it meticulously divides the downdraft gasifier into four distinct zones: the drying zone, where moisture content is reduced; the pyrolysis zone, where biomass undergoes thermal decomposition; the separation zone, where tar and other pyrolysis products are destined to different treatments; and the gasification zone, where syngas is produced. This granular approach enables a detailed analysis of each stage, facilitating a deeper understanding of the intricate gasification process. Furthermore, the model’s multi-scale nature incorporates parameters within the separation section, allowing for the simulation of molecular-level phenomena, such as the formation of preferential pathways. These pathways play a pivotal role in determining the composition of the resulting syngas, making the model exceptionally valuable for predicting and optimizing syngas quality. [ABSTRACT FROM AUTHOR]

The injection of hydrogen into the natural gas network can contribute to the large-scale integration of renewables, as hydrogen can be easily produced through electrolysis from wind or solar energy. However, the addition of hydrogen to natural gas influences fuel properties, asking for the assessment of the safe and efficient operation of existing end-user equipment, such as domestic burners and boilers. In this work, 3-dimensional resolved numerical simulations based on Computational Fluid Dynamics are carried out to shed light on the effect of H2 addition on the combustion process occurring in condensing boilers equipped with perforated cylindrical burners. To this purpose, multi-hole geometries emulating a portion of a perforated burner are analyzed. Since the burner holes are positioned very close to each other, the interaction of the adjacent laminar premixed flames is observed to occur with influence on the flow and thermo-chemical fields which differ from those of a single premixed flame. The addition of hydrogen was found to lead to an anticipation of the reaction zone, although the general features observed with the G222 gas (23% H2, 77% CH4 ) were alike those of the G20 gas (100% CH4).

Domestic condensing boilers are equipped with perforated burners ensuring short-length premixed flames issues from a series of circular holes and slits. Despite some efforts that have been devoted to understanding the effect of hole diameter, pattern, and hole-to-hole distance on the resulting flames, very little is known about the flames from a series of slits. In this work 3-dimensional numerical simulations with skeletal kinetic mechanisms are performed to determine the structure of premixed methane-air flames issuing from two-slits patterns, often recurring in practical burner designs, i.e. several equally-spaced slits and a group of four slits. The arrangement of the slits greatly influences the resulting flames. A significant change in the flame behaviour occurs depending on the inlet velocity; at low speeds, the flames issuing from the slits present a flat region, while increasing the speed they assume a conical shape along the slit length. Neighbour flames are distinct from each other at low speeds, while they interact strongly with increasing the velocity. Interestingly, a series of several slits produce a single long wedge-shaped flame, while the group of four slits generates a single conical flame. [ABSTRACT FROM AUTHOR]

Recycling lithium-ion batteries (LIBs) is becoming an imperative task given the large flow of spent batteries that in the next future will have to be managed. Among the current three main recycling routes to convert spent LIBs into recycled products, that is, pyrometallurgy, hydrometallurgy, or direct recycling, the co-precipitation route lies between the last two routes: its key unit operations are the leaching of battery materials and the co- precipitation of a precursor for the re-synthesis of the cathode active material (CAM). High susceptibility to impurities in the leached solution and a strong link between high-quality CAM precursors and the composition of the dissolved metal salts, makes experimental analysis on spent LIBs a crucial step to find the best operating conditions. For this reason, we present an experimental campaign to study the co-precipitation and formation of the complex chemical compounds involved in the process. Moreover, we also exploit the support that rigorous models are giving in many industrial fields, also benefiting chemical engineering and laboratory analysis. Therefore, in this study we also present a rigorous simulation model on UniSim Design® with the thermodynamic package OLI® that enables the possibility to consider most of the different liquid-solid equilibria needed. A validation of the model is performed with experimental data and a sensitivity analysis on metal concentrations, pH, and chelating agent is performed to find the critical parameters that regulate the co-precipitation outcomes. The aim is to optimize the choice of operating conditions to limit the number of laboratory tests and complex analyses that are often expensive and time-consuming. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have become a widespread technology for electrochemical energy storage in the current era of digitalization and transport electrification, being used as electric stationary storage as well as for powering electric vehicles, e-bikes and portable electronic devices such as smartphones and laptops. However, LIBs contain valuable materials, such as cobalt, nickel, lithium and graphite, whose supply has become critical to meet the increasing demand of batteries. Therefore, proper recycling processes are required in order to recover these materials from spent batteries and re-use them to produce new batteries in a sustainable cycle. This contribution provides an extensive survey of the main recycling routes available today, focusing specifically on pyrometallurgical and hydrometallurgical processes based in Europe, North America and Asia. Attention is also devoted to the recycling behaviour of individuals and companies and to the possible ways to increase their recycling rate. The comparison of different processes allows for the ranking of best practices as well as the drawbacks of different process units, with identification of which materials can be recovered, their recovery rate, and an assessment of the overall recycling efficiency of the process for different battery sizes (small and large, for portable electronics and electric vehicles, respectively). The analysis reveals that pyrometallurgical processes can flexibly treat different LIB chemistries but, since the electrolyte and graphite are burnt in the process, the global recycling efficiency cannot compete with hydrometallurgical processes, especially for small format batteries. Nevertheless, hydrometallurgical processes typically require preliminary mechanical separation treatments to separate the black mass, which contains valuable electrodic materials, as well as complex precipitation steps, which eventually reduce the material recovery rate and the applicability to diverse LIB chemistries. Finally, the study reports an analysis of the electrochemical performance of a battery made with recycled materials, showing that even if recycled cathodic materials had a lower gravimetric capacity and solid-state diffusivity, the performance of a recycled battery could be compensated by simple minor changes to the cell design which would ultimately decrease the specific energy density by a few percent compared to a LIB made with virgin materials. [ABSTRACT FROM AUTHOR]

Exhaust gas recirculation is a technique that allows for controlling the combustion chamber temperature and reducing the NOx and particle matter emissions. Moreover, it helps to mitigate soot formation and ash agglomeration in combustion systems. The present study investigated the effect of exhaust gas recirculation on combustion temperatures of a 140 kW underfed stoker biomass boiler. To this purpose, a wide range of operating conditions were used, collecting data regarding flue gas and fixed bed temperatures. It turned out that the recirculating ratio has a significant effect on the temperatures in the primary combustion zone, affecting the thermal gradient and the main thermal zones of the biomass combusting bed. The obtained results can be useful for lumped parameter modeling, or CFD validation purposes. [ABSTRACT FROM AUTHOR]

Nowadays, energy self-sufficiency cannot ignore the environmental sustainability of how it is achieved. On the other hand, one of the largest waste disposal components of a reclamation consortium is represented by residues derived from habitat maintenance. These residues are mainly formed by riparian vegetation that, from an energy point of view, can represent a renewable biomass. Some practical problems arise when passing from a theoretical approach to the development of an effective supply chain, the main of which is the biomass availability. Since the riparian ecosystem is characterized by a wide variety of landforms and biological communities, the functional supply chain must consider seasonal variability, different biomass composition depending on the land, and, hence, a mean biomass feedstock availability. The presented study has been conducted in a reclamation consortium of Northern Tuscany in Italy and examined the main characteristics of the feedstock and estimating its availability. This information has been used to propose different possible supply and utilization chains: a network of small-scale plants, biomass gasification involving external local utilizers or more complex scenarios dedicated to the production of syngas. Among the two final possible supply chains identified, gasification for syngas production and anaerobic digestion for biogas production, the first option resulted to be more profitable. The possible application to the consortium energy balance has been analyzed and commented, evidencing different technical factors that can influence its value. [ABSTRACT FROM AUTHOR]